First Measurement of Anisotropy with Stellar Intensity Interferometry and Associated Improvements to the VERITAS-SII Analysis
Loading...
Date
2025-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The Ohio State University
Abstract
This thesis presents an angular measurement of gamma Cassiopeiae using stellar intensity interferometry (SII) at VERITAS, the first successful measurement of the oblateness and orientation of a star with this technique. Gamma Cas is a rapidly rotating Be type star, spinning near its breakup velocity. Because of its extreme rotation speed, it has an oblate shape and a decretion disk of emitted material near its equator. We measure a major/minor axis ratio of 1.28 +/- 0.04, position angle 116 +/- 4 degrees, and minor axis angular diameter of 0.43 +/- 0.02 mas with a simple analytic uniform ellipse fit. By comparing the data with more complex stellar models, we measure an equatorial diameter of 0.605 (+0.041/-0.034) mas, rotational velocity 98.9 +/- 0.6% of breakup, and position angle 115 +/- 2 degrees. These agree well with expectations. This thesis also describes the general VERITAS-SII analysis with detailed improvements to measure gamma Cas, studies for understanding the random correlated background of the correlation function and its implications for SII measurements, and future plans for SII.
Description
Keywords
stellar intensity interferometry, gamma Cassiopeiae, angular diameter, bright stars, rapidly rotating stars